As a piezoelectric device used in various electronic devices represented by mobile communication equipment such as a cell-phone, a surface acoustic wave device (generically referred to as a “SAW device”), which is used as a SAW duplexer or a SAW filter, is generally used. Here, the surface acoustic wave device is explained as a typical example. However, the present invention can also be applied to other similar piezoelectric devices, and further, to various electronic parts in which functions are loaded on an insulating substrate. The surface acoustic wave device is mounted with an interdigital transducer (IDT) generally constituted by comb-shaped electrodes on one surface of a piezoelectric substrate (principal surface, corresponding to “other surface” in the embodiments and Claims described later), and the principal surface is covered with a ceiling layer (sealing layer or a sealing plate) to form a package.
In this type of surface acoustic wave device, a predetermined hollow portion is formed around (generally in an upper layer of) a comb-shaped electrode section (IDT) and the upper layer is sealed by the ceiling layer (sealing layer or sealing plate) together with the piezoelectric substrate, which is supplied to consumers as a packaged parts.
In the packaged parts, an external connection terminal for connection with an electronic device mounted on the piezoelectric substrate side or the ceiling layer side is formed. The external connection terminal is formed as disclosed in, for example, Patent Documents 1 to 3, in such a manner that a through-hole reaching the comb-shaped electrodes side (principal surface) is provided in the piezoelectric substrate or the ceiling layer, and an electrode post (through-hole electrode post) connected to the through-hole is formed to form an external connection electrode in an exposed portion of the through-hole electrode post (on an opposite side to the principal surface of the piezoelectric substrate: rear surface), and after the ceiling layer is stuck to the piezoelectric substrate and sealed, a gold (Au) bump or a solder bump is provided on the external connection electrode, thereby connecting with a terminal of an external circuit. Hereinafter, the external connection electrode may be referred to as an external connection terminal. Specifically, an anisotropic conductive layer or a solder ball is interposed between the external connection terminal and a mounting device or a connection terminal of a device, and is pressure bonded or heated and pressure bonded.
Moreover, in this type of piezoelectric device, rewiring is provided on the principal surface of the piezoelectric substrate, thereby enabling to realize three-dimensional lamination such as Chip to Chip (CTC), Chip to Wafer (CTW), and Wafer to Wafer (WTW).